I have a R9 Fury connected to a Dell U3415W and have tried various real resolutions and cannot find a way to make use of virtual super resolution. I understand that wide resolutions are not supported but something seems off. No matter what I do it always shows "not supported". this includes trying going all the way down to 1080p.

The reason i am trying to enable is to get more accurate test results for steam VR. My current results are very low, saying that it is due to my graphics card needing to be updated. Clearly this is not the case. After tons of research I found several recommendations including resetting Crimson settings to default, deleting/resetting shader cache, this is the only thing recommended that I have left to try that has been suggested to fix this issue yet I am not able to since it states it is not supported.

No as I stated in my original question. I am not able to turn it on as it shows as not supported. I have tried with GPU scaling turned on and off. I have also stated clearly that I have tried setting my target resolution to those that are listed in the supported section of the image you pasted for virtual super sampling. Thanks for your help.

Thanks but this does not answer my question or clarify things. If I set the resolution of my monitor to a listed supported resolution, regardless of the recommended resolution for my monitor should I be able to enable virtual super resolution?

Again, you have a supported resolution. The OP is being told in plain English that his monitor at the default/native resolution is not supported. As does the above chart, no matter how old it is. Not all resolutions are supported, and if his was, it would not say it is not.